Let's Play Command & Conquer One Remastered - GDI 15 A (Temple Strike) - Sarajevo West - Level 24
For me, this is the hardest level in the GDI campaign because there is so little Tiberian on the map that it soon becomes a war of attrition. Plus, there are respawning patrols, re-spawning buildings, and the enemy will happily attack your base and your harvester without provocation. That is why I had to pull out every trick in the book to beat this level.
Firstly, as you see in the video, I use the wall trick. The enemy still have figured out how to get past sand bags, so I eventually wall off half the map to keep the enemy in their base.
Then, I take over one of their silos and build a barracks. Whenever a silo is full, you can send in an engineer who will take the Tiberian and the building. Then, delete the silo, wait for another to be built, wait for it to fill up completely, and then take it over with an engineer again.
Also, I made heavy use of the Mammoth tanks because they regenerate their health up to half way, which means they can take damage and I do not have to waste precious credit on repairing them.